Package-on-Package Bonding With Interposer Flattening and Laser Soldering
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Solution Overview
Problem
The challenge in manufacturing package-on-package devices lies in the bonding process, particularly due to warpage of the interposer substrate, which can lead to bonding failures between the interposer and the bottom semiconductor package, causing misalignment and failure in the solder ball connection.
Innovation Solution
A method involving a pressing member to flatten the interposer substrate against the bottom semiconductor package, combined with a laser beam to melt and adhere the upper solder balls to the lower solder balls, ensuring proper alignment and bonding, and a bonding apparatus with a stage, optical system, and pressing member to manage the curvature of the interposer substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the interposer substrate is bonded to the bottom semiconductor package without pressing, then the bonding process is simpler, but warpage occurs causing misalignment and bonding failure of solder balls
Solution Approach 1:
The pressing member is introduced to preliminarily flatten the interposer substrate before the soldering process, preventing warpage-induced misalignment during bonding while maintaining process simplicity through automated integration
2Manufacturing precision
If a pressing member is used to flatten the interposer substrate, then solder ball alignment is improved, but the device complexity increases
Solution Approach 1:
The pressing member is designed to perform multiple functions: flattening the interposer substrate, maintaining contact pressure during soldering, and blocking the laser beam from reaching the bottom chip, thereby reducing the need for separate components and minimizing overall device complexity
3Temperature
If the laser beam is allowed to reach the bottom semiconductor chip, then the entire area is heated uniformly, but the bottom chip is damaged
Solution Approach 1:
The pressing member is designed with selective transparency: it blocks the laser beam in the central region where the bottom chip is located, while allowing the beam to pass through the peripheral regions where solder balls are positioned, achieving localized heating control that prevents chip damage while ensuring proper solder melting
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents bonding failures by ensuring accurate alignment and strong solder connections between the interposer and the bottom semiconductor package, enhancing the reliability and performance of the package-on-package device.
Implementation Method 1
irradiating the interposer substrate with a laser beam to adhere the lower solder balls to the upper solder balls
Implementation Method 2
adhering the second balls or bumps of solder respectively to the first balls or bumps of solder by melting the second balls or bumps of solder
Data Source
AI summary
A method of manufacturing a package-on-package device includes a bonding step carried out by a bonding apparatus including a pressing member and a light source that produces a laser beam. A bottom package including a lower substrate, lower solder balls alongside an edge of the lower substrate, and a lower chip on a center of the lower substrate is provided, the bottom package is bonded to an interposer substrate having upper solder balls aligned with the lower solder balls, and a top package having an upper substrate and an upper chip on the upper substrate is bonded to the interposer substrate. While the interposer substrate is disposed on the bottom package, the pressing member presses the interposer substrate against the bottom package, and the laser beam adheres the lower solder balls to the upper solder balls.